push an image in appsrc

[andre_th]

Hi,
I am following Gstreamer 0.10's tutorials in order to learn more about it.
I want to modify the tutorial number 8, teaching how to use "appsrc".
I want to feed a JPEG image instead of audio data and sink it in a v4l2sink
device dev/video0.
The following code doesn't work and gives the output:

Error received from element video_source: Internal data flow error.
Debugging information: gstbasesrc.c(2625): gst_base_src_loop ():
/GstPipeline:test-pipeline/GstAppSrc:video_source:
streaming task paused, reason not-negotiated (-4)

I am a novice so probably I am just doing some stupid error, so (beside
switch to Gstreamer1.0) does anyone have any suggestion? 
thanks!
andre_th

This is the code (I tried to modify the tutorial):

#include <gst/gst.h>
#include <string.h>
#include <cv.h>
#include <highgui.h>
#include <stdio.h>

#define VIDEO_CAPS
"video/x-raw-rgb,bpp=8,depth=8,width=640,height=360,framerate=1/1,red_mask=224,green_mask=28,blue_mask=3,endianness=1234;"
  
/* Structure to contain all our information, so we can pass it to callbacks
*/
guint64 imagecounter=1;

typedef struct _CustomData {
  GstElement *pipeline, *app_source;
  GstElement *video_convert, *video_sink;
  
  guint64 num_samples;   /* Number of samples generated so far (for
timestamp generation) */
  
  guint sourceid;        /* To control the GSource */
  
  GMainLoop *main_loop;  /* GLib's Main Loop */
} CustomData;
  
static gboolean push_data (CustomData *data) {
  GstBuffer *buffer;
  GstFlowReturn ret;
  gint8 *raw;
  gint num_samples; 
  gfloat freq;
  int depth,height,width,step,channels;
  guchar *data1;
  IplImage* img;
  g_print("push_data is beginning\n");
  

  img=cvLoadImage("frame1.jpg",CV_LOAD_IMAGE_COLOR); 
  height    = img->height;  
  width     = img->width;
  step      = img->widthStep;
  channels  = img->nChannels;
  depth     = img->depth;
  data1      = (guchar *)img->imageData;
  num_samples = height*width*channels;
  g_print("height %d\n",height);
  g_print("width %d\n",width);
  g_print("widthStep %d\n",step); 
  g_print("nChannels %d\n",channels);
  g_print("depth %d\n",depth);
  g_print("image_number %" G_GUINT64_FORMAT "\n", imagecounter);
  g_print("sizeof guchar: %lu\n",sizeof(guchar));

  /* Create a new empty buffer */
  buffer = gst_buffer_new_and_alloc (num_samples); // guint size :the size
in bytes of the new buffer's data.
  g_print("buffer initialized\n");

  /* Set its timestamp and duration */
  GST_BUFFER_TIMESTAMP (buffer) = gst_util_uint64_scale (imagecounter,
GST_SECOND, 1 );
  imagecounter += 1;
  
  
  memcpy( (guchar *)GST_BUFFER_DATA( buffer ), data1, GST_BUFFER_SIZE(
buffer ) );
  g_print("image data copied into buffer\n");
  data->num_samples += num_samples;
  
  /* Push the buffer into the appsrc */
  g_signal_emit_by_name (data->app_source, "push-buffer", buffer, &ret);
  g_print("buffer pushed\n");
  /* Free the buffer now that we are done with it */
  gst_buffer_unref (buffer);
  g_print("buffer unreferenced\n");
  if (ret != GST_FLOW_OK) {
     g_printerr("something wrong in sending data");
    /* We got some error, stop sending data */
    return FALSE;
  }
  g_print("push_data is ending\n");
  return TRUE;
}
  
/* This signal callback triggers when appsrc needs data. Here, we add an
idle handler
 * to the mainloop to start pushing data into the appsrc */
static void start_feed (GstElement *source, guint size, CustomData *data) {
  if (data->sourceid == 0) {
    g_print ("Start feeding\n");
    data->sourceid = g_idle_add ((GSourceFunc) push_data, data);
    g_print ("push_data started\n");
  }
}
  
/* This callback triggers when appsrc has enough data and we can stop
sending.
 * We remove the idle handler from the mainloop */
static void stop_feed (GstElement *source, CustomData *data) {
  if (data->sourceid != 0) {
    g_print ("Stop feeding\n");
    g_source_remove (data->sourceid);
    data->sourceid = 0;
  }
}
 
  
/* This function is called when an error message is posted on the bus */
static void error_cb (GstBus *bus, GstMessage *msg, CustomData *data) {
  GError *err;
  gchar *debug_info;
  
  /* Print error details on the screen */
  gst_message_parse_error (msg, &err, &debug_info);
  g_printerr ("Error received from element %s: %s\n", GST_OBJECT_NAME
(msg->src), err->message);
  g_printerr ("Debugging information: %s\n", debug_info ? debug_info :
"none");
  g_clear_error (&err);
  g_free (debug_info);
  
  g_main_loop_quit (data->main_loop);
}
  
int main(int argc, char *argv[]) {
  CustomData data;
  gchar *video_caps_text;
  GstCaps *video_caps;
  GstBus *bus;
  
  /* Initialize cumstom data structure */
  memset (&data, 0, sizeof (data));
  
  /* Initialize GStreamer */
  gst_init (&argc, &argv);
  
  /* Create the elements */
  data.app_source = gst_element_factory_make ("appsrc", "video_source");
  data.video_convert = gst_element_factory_make ("ffmpegcolorspace", "csp");
  data.video_sink = gst_element_factory_make ("v4l2sink", "video_sink");

  /* Create the empty pipeline */
  data.pipeline = gst_pipeline_new ("test-pipeline");
  
  if (!data.pipeline || !data.app_source || !data.video_convert ||
!data.video_sink) {
    g_printerr ("Not all elements could be created.\n");
    return -1;
  }

  /* Configure appsrc */
  video_caps_text = g_strdup_printf (VIDEO_CAPS);
  video_caps = gst_caps_from_string (video_caps_text);
  if( !GST_IS_CAPS(video_caps) ) {
                g_printerr("Error creating Caps for OpenCV-Source,
exiting...");
                exit( 1 );
            }
  g_object_set (data.app_source, "caps", video_caps, NULL);
  g_signal_connect (data.app_source, "need-data", G_CALLBACK (start_feed),
&data);
  g_signal_connect (data.app_source, "enough-data", G_CALLBACK (stop_feed),
&data);
  
  /* Configure v4l2loopback videosink*/
  g_object_set (data.video_sink, "device", "/dev/video0", NULL);

  /* Link all elements that can be automatically linked because they have
"Always" pads */
gst_bin_add_many (GST_BIN (data.pipeline),
data.app_source,data.video_convert, data.video_sink, NULL);

if ( gst_element_link_many ( data.app_source,
data.video_convert,data.video_sink, NULL) != TRUE) {
    g_printerr ("Elements could not be linked.\n");
    gst_object_unref (data.pipeline);
    return -1;}
/* 

  /* Instruct the bus to emit signals for each received message, and connect
to the interesting signals */
  bus = gst_element_get_bus (data.pipeline);
  gst_bus_add_signal_watch (bus);
  g_signal_connect (G_OBJECT (bus), "message::error", (GCallback)error_cb,
&data);
  gst_object_unref (bus);
  
  /* Start playing the pipeline */
  gst_element_set_state (data.pipeline, GST_STATE_PLAYING);
  
  /* Create a GLib Main Loop and set it to run */
  data.main_loop = g_main_loop_new (NULL, FALSE);
  g_main_loop_run (data.main_loop);
  
  /* Free resources */
  gst_element_set_state (data.pipeline, GST_STATE_NULL);
  gst_object_unref (data.pipeline);
  return 0;
}




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